High specific power electric motor is a key enabling technology for electric/hybrid-electric propulsion for aircraft. High-frequency, 'air-core' machine topologies show potential for high specific power when the machines are integrated within jet engines at high speed, e.g. 15,000 rpm. In this paper, we explore how these machines scale to electric propulsion systems at a range of speeds, to also include 'boundary layer ingestion' fan in newly proposed Single-aisle Turboelectric Aircraft with an Aft Boundary-Layer (STARC-ABL) propulsors. Detailed analytical models that have been experimentally verified, and an evolutionary genetic algorithm are utilized to study the effect of speed on weight of the topology. The results show that the topology, especially with proper selection of support structure design, maintains high specific power even at lower speeds. Furthermore, a case study shows that rim-driven fan topology is favorable for the boundary layer ingestion fan.